In modern consumer electronics, audio capability is playing an increasingly larger role as improvements in digital audio signal processing and audio content delivery continue to happen. There is a range of consumer electronics devices that are not dedicated or specialized audio playback devices such as smart phones and portable timepieces, yet can benefit from improved audio performance. These devices, however, often do not have sufficient space to house high fidelity speakers. This is also true for portable personal computers such as laptop, notebook, and tablet computers, and, to a lesser extent, desktop personal computers with built-in speakers. Such devices typically require speaker enclosures or boxes that have a relatively low rise (i.e. height as defined along the z-axis) and small back volume, as compared to, for instance, stand alone high fidelity speakers and dedicated digital music systems for handheld media players.
The drivers (speakers) for such devices therefore typically use a low profile diaphragm assembly, which is composed of a diaphragm or sound radiating surface (SRS), a voice coil and optional former or bobbin for connecting the voice coil to the SRS, and a suspension member for suspending the entire assembly from a frame. The voice coil causes the SRS to vibrate axially thereby creating pressure waves outside the driver enclosure. The suspension surrounds and suspends the SRS within the enclosure and allows it to vibrate axially. Each of these moving parts, however, have natural structural resonances that can be excited at certain frequencies, which may be different from one another. As a result, at certain frequencies the suspension member moves out of phase, or the SRS itself may move non-pistonically (so-called “break up frequencies”. Such out of phase movements can result in an undesirable sound pressure output (i.e. drop or peak in pressure) at these resonant frequencies. In addition, the voice coil may generate a heat output that can cause a distortion in the acoustic output if not dissipated.